The suggestion that £2172 is expensive puts a very low value on your life
That would be true if there were high chances of it saving your life. How many mid-airs have there been recently in the UK. There was the recent helicopter/C152 crash in the UK, then the air cadets a few years back. Wasn't there a collision between a microlight and another aircraft a few years back too?
I don't know how exhaustive this list is:
https://en.wikipedia.org/wiki/List_o..._Kingdom#2010s
but it suggests civilian mid-air collisions aren't that common. Let's say for the sake of argument that an infallible early warning device could save 1 life a year and there are 14000 active GA aircraft in the UK, all of which need devices to be fitted. The unit may cost £2k, but it'll probably average £3k by the time it's installed. The average device lifetime is 15 years.
14000*3000/15 = 2.8 million pounds per life saved. To be honest, I think I'm probably being significantly generous to the devices.
The NHS aims to buy one quality-adjusted-life-year for about 20-30K, so if the average pilot has 40 years of life ahead of him/her then a life-saving treatment that cost 1.2 million or more would be judged uncost effective. I believe that there's a threshold around the 2 million mark per life saved as to when improvements to roads become cost-effective.
Public health economics isn't something I know a great deal about, so feel free to adjust the assumptions or correct my methodology. But my point is that it's not obvious that a system at this price is good value for money. If you spent the money elsewhere (perhaps on more training, or on running shoes for jogging) it would probably do more good.